Optical Device

ABSTRACT

An optical device is disclosed herein. In some embodiments, an optical device includes a first outer substrate, a second outer substrate, a liquid crystal element positioned between the first outer substrate and the second outer substrate, a first intermediate layer between the first outer substrate and the liquid crystal element, and a second intermediate layer between the second outer substrate and the liquid crystal element, wherein a sum of total thicknesses of the first and second intermediate layers is 800 μm or more, and wherein the liquid crystal element includes a first base layer, a second base layer, a liquid crystal layer between the first base layer and the second base layer, a pressure-sensitive adhesive layer between the first base layer and the liquid crystal layer, and a spacer to maintain a gap between the first and second base layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. § 371of International Application No. PCT/KR2021/015293, filed on Oct. 28,2021, which claims priority from Korean Patent Application No.10-2020-0142093 dated Oct. 29, 2020, the disclosures of which areincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to an optical device.

BACKGROUND ART

For long-term stability and large-area scalability of a liquid crystalcell using flexible substrates, it is important that a cell gap ismaintained between upper and lower substrates and adhesion force isimparted between the upper and lower substrates.

In Non-Patent Document 1 (“Tight Bonding of Two Plastic Substrates forFlexible LCDs” SID Symposium Digest, 38, pp. 653-656 (2007)), atechnique for forming an organic film pattern in the form of a column orwall with a cell gap height on one substrate and fixing it to theopposite substrate using an adhesive is disclosed. However, in such atechnique, the adhesive must be located only on the column surface orwall surface, but the technique of micro-stamping the adhesive on thecolumn surface or wall surface has high process difficulty; the controlof the adhesive thickness and area is difficult; upon lamination of theupper and lower substrates, there is a high probability that theadhesive will be pushed out; and there is a risk that the adhesive maybe contaminated into the alignment film or liquid crystal.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional diagram of an exemplary optical device ofthe present disclosure.

FIG. 2 is a cross-sectional diagram of an exemplary liquid crystalelement of the present disclosure.

FIGS. 3A and 3B are a photographs of the optical device of ComparativeExample 1.

DISCLOSURE Technical Problem

In order that the cell gap of the liquid crystal cell is maintained andthe attachment force is secured between the upper substrate and thelower substrate, it may be considered that a spacer and an alignmentfilm are formed on the lower substrate and a pressure-sensitive adhesivelayer having both liquid crystal orientation force and adhesion force isformed on the upper substrate, followed by lamination. However, such astructure is vulnerable to external pressures due to the very lowmodulus of the pressure-sensitive adhesive layer, whereby it isdifficult to obtain a good appearance quality in an autoclave process athigh temperatures and high pressures. Specifically, when the structuralstability of the liquid crystal cell is not ensured in the autoclaveprocess, defects such as cell gap collapse, or flowing/crowding of theliquid crystals occur, which cause a decrease in the electro-opticalproperties and appearance uniformity of the liquid crystal cell.

The present disclosure provides an optical device that can ensurestructural stability and good quality uniformity by maintaining the cellgap of the liquid crystal cell properly, having excellent attachmentforce between the upper substrate and the lower substrate, andminimizing defects such as pressing or crowding.

Technical Solution

Among the physical properties mentioned in this specification, when themeasured temperature affects the results, the relevant physical propertyis a physical property measured at room temperature, unless otherwisespecified. The term room temperature is a natural temperature withoutheating or cooling, which is usually a temperature in the range of about10° C. to 30° C., or about 23° C. or about 25° C. or so. In addition,unless otherwise specified in the specification, the unit of temperatureis ° C. Among the physical properties mentioned in this specification,when the measured pressure affects the results, the relevant physicalproperty is a physical property measured at normal pressure, unlessotherwise specified. The term normal pressure is a natural pressurewithout pressurization or depressurization, where usually about 1atmosphere or so is referred to as normal pressure.

The present disclosure relates to an optical device. FIG. 1 exemplarilyshows an optical device of the present disclosure. As shown in FIG. 1 ,the optical device may comprise a first outer substrate (100 a), asecond outer substrate (100 b) disposed opposite to the first outersubstrate (100 a), and a liquid crystal element (300) positioned betweenthe first and second outer substrates. The optical device may compriseat least one or more intermediate layers positioned between the firstouter substrate and the liquid crystal element and between the secondouter substrate and the liquid crystal element. FIG. 1 exemplarily showsan optical device comprising intermediate layers (200 a, 200 b)positioned between a first outer substrate (100 a) and a liquid crystalelement (300) and between the second outer substrate (100 b) and theliquid crystal element (300), respectively.

The first outer substrate and the second outer substrate may eachindependently be an inorganic substrate or a plastic substrate. Awell-known inorganic substrate may be used as the inorganic substratewithout any particular limitation. In one example, a glass substratehaving excellent light transmittance may be used as the inorganicsubstrate. As an example of the glass substrate, a soda lime glasssubstrate, a general tempered glass substrate, a borosilicate glasssubstrate or an alkali-free glass substrate, and the like may be used,without being limited thereto. As the polymer substrate, a cellulosefilm such as TAC (triacetyl cellulose) or DAC (diacetyl cellulose); aCOP (cyclo olefin copolymer) film such as norbornene derivatives; anacrylic film such as PA (polyacrylate) or PMMA (poly(methylmethacrylate); a PC (polycarbonate) film; a polyolefin film such as PE(polyethylene) or PP (polypropylene); a PVA (polyvinyl alcohol) film; aPI (polyimide) film; a sulfone-based film such as a PSF (polysulfone)film, a PPS (polyphenylsulfone) film or a PES (polyethersulfone) film; aPEEK (polyetheretherketon) film; a PEI (polyetherimide) film; apolyester-based film such as a PEN (polyethylenenaphthatlate) film or aPET (polyethyleneterephtalate) film; or a fluororesin film, and the likemay be used, without being limited thereto. In each of the first outersubstrate and the second outer substrate, a coating layer of: gold;silver; or a silicon compound such as silicon dioxide or siliconmonoxide, or a functional layer such as an antireflection layer may alsobe present as needed.

In one example, the first outer substrate and/or the second outersubstrate may be a glass substrate. In order to overcome the physicallimitations of the liquid crystal element, glass substrates may belaminated to both sides of the liquid crystal element, or a glasssubstrate may be laminated to one side of the liquid crystal element anda film substrate may be laminated to the other side of the liquidcrystal element, in the automobile or window industry. In the automobileindustry thereof, there is a demand for a process of laminating glasssubstrates to both sides of a liquid crystal element via an adhesivelayer. However, the liquid crystal element is vulnerable to externalpressures due to the use of the pressure-sensitive adhesive layer, sothat defects such as cell gap collapse, or flowing or crowding of theliquid crystals may occur in a glass substrate laminating process suchas the autoclave at high temperatures and high pressures. According tothe present invention, as described below, the thicknesses of theintermediate layers are controlled, whereby the defects can beminimized, and the structural stability and the quality uniformity ofthe optical device can be secured.

The first outer substrate and the second outer substrate may each have athickness of about 0.3 mm or more. In another example, the thickness maybe about 0.5 mm or more, 1 mm or more, 1.5 mm or more, or about 2 mm ormore, and may also be about 10 mm or less, 9 mm or less, 8 mm or less, 7mm or less, 6 mm or less, 5 mm or less, 4 mm or less, or about 3 mm orless.

The first outer substrate and the second outer substrate may be a flatsubstrate or may be a substrate having a curved surface shape. Forexample, the first outer substrate and the second outer substrate may besimultaneously flat substrates, simultaneously have a curved surfaceshape, or any one may be a flat substrate and the other may be asubstrate having a curved surface shape. In addition, here, in the caseof having the curved surface shape at the same time, the respectivecurvatures or curvature radii may be the same or different. In thisspecification, the curvature or curvature radius may be measured in amanner known in the industry, and for example, may be measured using acontactless apparatus such as a 2D profile laser sensor, a chromaticconfocal line sensor or a 3D measuring confocal microscopy. The methodof measuring the curvature or curvature radius using such an apparatusis known.

With respect to the first outer substrate and the second outersubstrate, for example, when the curvatures or curvature radii on thefront surface and the back surface are different, the respectivecurvatures or curvature radii of the opposing surfaces, that is, thecurvature or curvature radius of the surface facing the second outersubstrate in the case of the first outer substrate and the curvature orcurvature radius of the surface facing the first outer substrate in thecase of the second outer substrate may be a reference. Furthermore, whenthe relevant surface has portions that the curvatures or curvature radiiare not constant and different, the largest curvature or curvatureradius may be a reference, or the smallest curvature or curvature radiusmay be a reference, or the average curvature or average curvature radiusmay be a reference.

The first outer substrate and the second outer substrate may each have adifference in curvature or curvature radius within about 10%, within 9%,within 8%, within 7%, within 6%, within 5%, within 4%, within 3%, within2% or within about 1%. When a large curvature or curvature radius is CLand a small curvature or curvature radius is CS, the difference incurvature or curvature radius is a value calculated by 100%×(CL-CS)/CS.In addition, the lower limit of the difference in curvature or curvatureradius is not particularly limited. Since the differences in curvaturesor curvature radii of the first and second outer substrates can be thesame, the difference in curvature or curvature radius may be about 0% ormore, or more than about 0%. The control of such a curvature orcurvature radius is useful in a structure in which a liquid crystalelement contacts the intermediate layers as in the optical device of thepresent disclosure. That is, when the difference in the curvature orcurvature radius exceeds 10%, a problem in which the bonded outersubstrates are spread due to deterioration of bonding force may occur atthe time when the outer substrates and the liquid crystal element are incontact with the intermediate layers to be described below. However, ifit is controlled within 10%, it is possible to effectively prevent theproblem that the bonded outer substrates are spread due to deteriorationof the bonding force.

The first outer substrate and the second outer substrate may have thesame curvature sign. In other words, the first and second outersubstrates may be bent in the same direction. That is, in the abovecase, both the center of curvature of the first outer substrate and thecenter of curvature of the second outer substrate exist in the sameportion of the upper part and the lower part of the first and secondouter substrates. When the first and second outer substrates are bent inthe same direction, the first and second outer substrates can be moreefficiently bonded by the intermediate layers, and after bonding, thebonding force deterioration of the first and second outer substrates andthe liquid crystal element and/or the polarizer can be prevented moreeffectively.

The specific range of each curvature or curvature radius of the firstouter substrate and the second outer substrate is not particularlylimited. In one example, the curvature radius of each of the first andsecond outer substrates may be about 100 R or more, 200 R or more, 300 Ror more, 400 R or more, 500 R or more, 600 R or more, 700 R or more, 800R or more, or about 900 R or more, or may be about 10,000 R or less,9,000 R or less, 8,000 R or less, 7,000 R or less, 6,000 R or less,5,000 R or less, 4,000 R or less, 3,000 R or less, 2,000 R or less,1,900 R or less, 1,800 R or less, 1,700 R or less, 1,600 R or less,1,500 R or less, 1,400 R or less, 1,300 R or less, 1,200 R or less,1,100 R or less, or about 1,050 R or less. Here, R means the degree ofcurvature of a circle having a radius of 1 mm. Thus, here, for example,100 R is the degree of curvature of a circle having a radius of 100 mmor the curvature radius for such a circle. The first and second outersubstrates may have the same or different curvature radii in the aboverange. In one example, when the curvatures of the first and second outersubstrates are different from each other, the curvature radius of thesubstrate having a large curvature among them may be within the aboverange. In one example, when the curvatures of the first and second outersubstrates are different from each other, a substrate having a largecurvature among them may be a substrate that is disposed in the gravitydirection upon using the optical device. When the curvature or curvatureradius of the first and second outer substrates is controlled as above,the net force, which is the sum of the restoring force and the gravity,may act to prevent the widening, even if the bonding force by theintermediate layer to be described below is decreased.

In one example, the optical device may not comprise polarizers betweenthe first outer substrate and the liquid crystal element and between thesecond outer substrate and the liquid crystal element. In anotherexample, the optical device may further comprise a polarizer in at leastone of positions between the first outer substrate and the liquidcrystal element and between the second outer substrate and the liquidcrystal element.

In this specification, the term polarizer means a film, sheet or elementhaving a polarization function. The polarizer is a functional elementcapable of extracting light vibrating in one direction from incidentlight vibrating in multiple directions.

The polarizer may be an absorption type polarizer or a reflection typepolarizer. In this specification, the absorption type polarizer means anelement showing selective transmission and absorption characteristicswith respect to incident light. The polarizer may transmit, for example,light vibrating in any one direction from incident light vibrating inmultiple directions, and may absorb light vibrating in the otherdirections. In this specification, the reflection type polarizer meansan element showing selective transmission and reflection characteristicswith respect to incident light. The polarizer may transmit, for example,light vibrating in any one direction from incident light vibrating inmultiple directions, and may reflect light vibrating in the otherdirections. According to one example of the present disclosure, thepolarizer may be an absorption type polarizer.

The polarizer may be a linear polarizer. In this specification, thelinear polarizer means a case in which the selectively transmitted lightis linearly polarized light vibrating in any one direction, and theselectively absorbed or reflected light is linearly polarized lightvibrating in a direction perpendicular to the vibration direction of thelinearly polarized light. In the case of the absorption type linearpolarizer, the light transmission axis and the light absorption axis maybe perpendicular to each other. In the case of the reflection typelinear polarizer, the light transmission axis and the light reflectionaxis may be perpendicular to each other.

In one example, the polarizers may each be a stretched polymer film dyedwith iodine or an anisotropic dye. As the stretched polymer film, a PVA(poly(vinyl alcohol)) stretched film may be exemplified. In anotherexample, each of the first polarizer and the second polarizer may be aguest-host type polarizer in which a liquid crystal polymerized in anoriented state is a host, and an anisotropic dye arranged according tothe orientation of the liquid crystal is a guest. In another example,the polarizers may each be a thermotropic liquid crystal film or alyotropic liquid crystal film.

A protective film, an antireflection film, a retardation film, apressure-sensitive adhesive layer, an adhesive layer, a surfacetreatment layer, and the like may be additionally formed on one side orboth sides of the polarizers, respectively. The retardation film may be,for example, a ¼ wave plate or a ½ wave plate. The ¼ wave plate may havean in-plane retardation value for light having a wavelength of 550 nm ina range of about 100 nm to 180 nm, 100 nm or 150 nm. The ½ wave platemay have an in-plane retardation value for light having a wavelength of550 nm in a range of about 200 nm to 300 nm or 250 nm to 300 nm. Theretardation film may be, for example, a stretched polymer film or aliquid crystal polymerization film.

The transmittance of each of the polarizers for light having awavelength of 550 nm may be in a range of 40% to 50%. The transmittancemay mean single transmittance of the polarizer for light having awavelength of 550 nm. The single transmittance of the polarizer can bemeasured using, for example, a spectrometer (V7100, manufactured byJasco). For example, after the air is set to the base line in a statewhere the polarizer sample (not including the upper and lower protectivefilms) is placed on the apparatus and each transmittance is measured ina state in which the axis of the polarizer sample is vertically andhorizontally aligned with the axis of the reference polarizer, thesingle transmittance can be calculated.

When it is assumed that the blocking state is implemented in the firstorientation state of the liquid crystal element, the polarizers may bedisposed in the optical device such that the angle formed by the averageoptical axis (vector sum of optical axes) of the first orientation stateand the light absorption axis of the polarizer is about 80 degrees toabout 100 degrees or about 85 degrees to about 95 degrees, orapproximately vertical, or may be disposed in the optical device suchthat it is 35 degrees to about 55 degrees or about 40 degrees to about50 degrees, or approximately 45 degrees.

FIG. 2 exemplarily shows a liquid crystal element. As shown in FIG. 2 ,the liquid crystal element may comprise a first base layer (10 a), apressure-sensitive adhesive layer (10 c) formed on the inside of thefirst base layer, a second base layer (20 a) disposed opposite to thefirst base layer (10 a), a spacer (20 c) formed on the inside of thesecond base layer (20 a) and a liquid crystal layer (30) positionedbetween the first base layer (10 a) and the second base layer (20 a).

As the first base layer and the second base layer, for example, aninorganic film such as a glass film, a crystalline or amorphous siliconfilm or a quartz or ITO (indium tin oxide) film, or a polymer film maybe used, and in terms of implementing flexible elements, a polymer filmmay be used.

In one example, each of the first base layer and the second base layermay be a polymer film. As the polymer film, TAC (triacetyl cellulose);COPs (cyclo olefin copolymers) such as norbornene derivatives; PMMA(poly(methyl methacrylate); PC (polycarbonate); PE (polyethylene); PP(polypropylene); PVA (polyvinyl alcohol); DAC (diacetyl cellulose); Pac(polyacrylate); PES (poly ether sulfone); PEEK (polyetheretherketon);PPS (polyphenylsulfone), PEI (polyetherimide); PEN(polyethylenenaphthatlate); PET (polyethyleneterephtalate); PI(polyimide); PSF (polysulfone); PA (polyarylate) or an amorphousfluororesin, and the like may be used, without being limited thereto. Inthe first base layer and the second base layer, a coating layer of gold,silver or a silicon compound such as silicon dioxide or siliconmonoxide, or a functional layer such as an antireflection layer may alsobe present as needed.

The first base layer and the second base layer may each have a thicknessof about 10 μm to about 1,000 μm. As another example, the base layersmay each have a thickness of about μm or more, 40 μm or more, 60 μm ormore, 80 μm or more, 100 μm or more, 120 μm or more, 140 μm or more, 160μm or more, or about 180 μm or more, and may be about 900 μm or less,800 μm or less, 700 μm or less, 600 μm or less, 500 μm or less, or about400 μm or less. When the thicknesses of the first base layer and thesecond base layer satisfy the above range, it is possible to reduceappearance defects such as wrinkles at the time of manufacturing anoptical device by laminating the liquid crystal element with outersubstrates.

The pressure-sensitive adhesive layer may be present on the innersurface of the first base layer. In this specification, the “innersurface” of the constitution included in the liquid crystal element maymean a surface facing the liquid crystal layer.

The pressure-sensitive adhesive layer may be optically transparent. Thepressure-sensitive adhesive layer may have average transmittance ofabout 80% or more, 85% or more, 90% or more, or 95% or more for thevisible light region, for example, a wavelength of 380 nm to 780 nm.

The pressure-sensitive adhesive layer may be a liquid crystalorientational pressure-sensitive adhesive layer. The pressure-sensitiveadhesive layer may be, for example, a vertically orientationalpressure-sensitive adhesive layer or a horizontally orientationalpressure-sensitive adhesive layer. In this specification, the“vertically orientational pressure-sensitive adhesive” may mean apressure-sensitive adhesive having attachment force capable of bodingthe upper substrate and the lower substrate while imparting verticalorientation force to the adjacent liquid crystal compound. In thisspecification, the “horizontally orientational pressure-sensitiveadhesive” may mean a pressure-sensitive adhesive having attachment forcecapable of bonding the upper substrate and the lower substrate whileimparting horizontal orientation force to the adjacent liquid crystalcompound. The pretilt angle of the adjacent liquid crystal compound withrespect to the vertically orientational pressure-sensitive adhesive maybe in a range of 80 degrees to 90 degrees, 85 degrees to 90 degrees orabout 87 degrees to 90 degrees, and the pretilt angle of the adjacentliquid crystal compound with respect to the horizontally orientationalpressure-sensitive adhesive may be in a range of 0 degrees to 10degrees, 0 degrees to 5 degrees or 0 degrees to 3 degrees.

In this specification, the pretilt angle may mean an angle formed by adirector of a liquid crystal compound with respect to a plane horizontalto a liquid crystal orientational pressure-sensitive adhesive or analignment film in a state where no voltage is applied. In thisspecification, the director of the liquid crystal compound may mean theoptical axis or the slow axis of the liquid crystal layer.Alternatively, the director of the liquid crystal compound may mean along axis direction when the liquid crystal compound has a rod shape,and may mean an axis parallel to the normal direction of the disk planewhen the liquid crystal compound has a discotic shape.

The thickness of the pressure-sensitive adhesive layer may be, forexample, in a range of 3 μm to 15 μm. When the thickness of thepressure-sensitive adhesive layer is within the above range, it may beadvantageous to minimize defects such as pressing or crowding of thepressure-sensitive adhesive when used in the manufacture of a liquidcrystal element, while securing attachment force between the uppersubstrate and the lower substrate.

As the pressure-sensitive adhesive layer, various types ofpressure-sensitive adhesives known in the industry as a so-called OCA(optically clear adhesive) may be appropriately used. Thepressure-sensitive adhesive may be different from an OCR (opticallyclear resin) type adhesive which is cured after the object to beattached is bonded in that it is cured before the object to be attachedis bonded. As the pressure-sensitive adhesive, for example, an acrylic,silicone-based, epoxy-based or urethane-based pressure-sensitiveadhesive may be applied.

The pressure-sensitive adhesive layer may comprise a cured product of apressure-sensitive adhesive resin. In one example, thepressure-sensitive adhesive layer may comprise a silicone-basedpressure-sensitive adhesive. The silicone pressure-sensitive adhesivemay comprise a cured product of a curable silicone compound as thepressure-sensitive adhesive resin.

The type of the curable silicone compound is not particularly limited,and for example, a heat-curable silicone compound or anultraviolet-curing silicone compound may be used. The curable siliconecompound may be referred to as a pressure-sensitive adhesive resin.

In one example, the curable silicone compound may be an addition-curingsilicone compound.

Specifically, the addition-curing silicone compound may be exemplifiedby (1) an organopolysiloxane containing two or more alkenyl groups inthe molecule and (2) an organopolysiloxane containing two or moresilicon-bonded hydrogen atoms in the molecule, but is not limitedthereto. Such a silicone compound can form a cured product by additionreaction, for example, in the presence of a catalyst to be describedbelow.

A more specific example of the (1) organopolysiloxane, which can be usedin the present disclosure, may include adimethylsiloxane-methylvinylsiloxane copolymer blocking withtrimethylsiloxane groups at both ends of the molecular chain, amethylvinylpolysiloxane blocking with trimethylsiloxane groups at bothends of the molecular chain, adimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymerblocking with trimethylsiloxane groups at both ends of the molecularchain, a dimethylpolysiloxane blocking with dimethylvinylsiloxane groupsat both ends of the molecular chain, a methyl vinylpolysiloxane blockingwith dimethylvinylsiloxane groups at both ends of the molecular chain, adimethylsiloxane-methylvinylsiloxane copolymer blocking withdimethylvinylsiloxane groups at both ends of the molecular chain, adimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymerblocking with dimethylvinylsiloxane groups at both ends of the molecularchain, an organopolysiloxane copolymer comprising a siloxane unitrepresented by R¹ ₂SiO_(1/2) and a siloxane unit represented by R¹ ₂R²SiO_(1/2) and a siloxane unit represented by SiO_(4/2), anorganopolysiloxane copolymer comprising a siloxane unit represented byR¹ ₂R²SiO_(1/2) and a siloxane unit represented by SiO_(4/2), anorganopolysiloxane copolymer comprising a siloxane unit represented byR¹R²SiO_(2/2) and a siloxane unit represented by R¹SiO_(3/2) or asiloxane unit represented by R²SiO_(3/2), and a mixture of two or moreof the foregoing, but is not limited thereto. Here, R¹is a hydrocarbongroup other than an alkenyl group, specifically, an alkyl group such asa methyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group or a heptyl group; an aryl group such as a phenylgroup, a tolyl group, a xylyl group or a naphthyl group; an aralkylgroup such as a benzyl group or a phenetyl group; a halogen-substitutedalkyl group such as a chloromethyl group, a 3-chloropropyl group, or a3,3,3-trifluoropropyl group, and the like. In addition, here, R²is analkenyl group, which may be, specifically, a vinyl group, an allylgroup, a butenyl group, a pentenyl group, a hexenyl group or a heptenylgroup, and the like.

A more specific example of the (2) organopolysiloxane, which can be usedin the present disclosure, may include a methylhydrogenpolysiloxaneblocking with trimethylsiloxane groups at both ends of the molecularchain, a dimethylsiloxane-methylhydrogen copolymer blocking withtrimethylsiloxane groups at both ends of the molecular chain, adimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymerblocking with trimethylsiloxane groups at both ends of the molecularchain, a dimethylpolysiloxane blocking with dimethylhydrogensiloxanegroups at both ends of the molecular chain, adimethylsiloxane-methylphenylsiloxane copolymer blocking withdimethylhydrogensiloxane groups at both ends of the molecular chain, amethylphenylpolysiloxane blocking with dimethylhydrogensiloxane groupsat both ends of the molecular chain, an organopolysiloxane copolymercomprising a siloxane unit represented by R¹ ₃SiO_(1/2), a siloxane unitrepresented by R¹ ₂HSiO_(1/2) and a siloxane unit represented bySiO_(4/2), an organopolysiloxane copolymer comprising a siloxane unitrepresented by R¹ ₂HSiO_(1/2) and a siloxane unit represented bySiO_(4/2), an organopolysiloxane copolymer comprising a siloxane unitrepresented by R¹HSiO_(2/2) and a siloxane unit represented byR¹SiO_(3/2) or a siloxane unit represented by HSiO_(3/2) and a mixtureof two or more of the foregoing, but is not limited thereto. Here, R¹isa hydrocarbon group other than an alkenyl group, which may be,specifically, an alkyl group such as a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group or a heptylgroup; an aryl group such as a phenyl group, a tolyl group, a xylylgroup or a naphthyl group; an aralkyl group such as a benzyl group or aphenetyl group; a halogen-substituted alkyl group such as a chloromethylgroup, a 3-chloropropyl group or a 3,3,3-trifluoropropyl group, and thelike.

When the pressure-sensitive adhesive layer is a vertical orientationpressure-sensitive adhesive layer, the pressure-sensitive adhesive mayhave a surface energy of 16 mN/m or less. The lower limit of the surfaceenergy may be, for example, 5 mN/m or more. When the pressure-sensitiveadhesive layer is a horizontal orientation pressure-sensitive adhesivelayer, the surface energy may be greater than 16 mN/m. The upper limitof the surface energy may be, for example, 50 mN/m or less. The surfaceenergy can be measured using a drop shape analyzer (KRUSS' DSA100product). Specifically, a process that deionized water with a knownsurface tension is dropped on the surface of the pressure-sensitiveadhesive to obtain the contact angle is repeated 5 times, therebyobtaining the average value of the resulting five contact angle values,and equally a process that diiodomethane with a known surface tension isdropped thereon to obtain the contact angle is repeated 5 times, therebyobtaining the average value of the resulting five contact angle values.Then, the surface energy was obtained by substituting a numerical value(Strom value) for the surface tension of the solvent by theOwens-Wendt-Rabel-Kaelble method using the obtained average values ofthe contact angles for deionized water and diiodomethane. The surfaceenergy (γsurface) of the sample can be calculated by considering thedispersion force between nonpolar molecules and the interaction forcebetween polar molecules (γsurface=γdispersion+γpolar), where the ratioof the polar term (γpolar) in the surface energy γsurface can be definedas polarity of the surface.

The upper substrate and the lower substrate of the liquid crystalelement may be attached to each other by a pressure-sensitive adhesivelayer. Specifically, the pressure-sensitive adhesive layer of the uppersubstrate and the spacer of the lower substrate may be attached to eachother. When the alignment film is formed on the spacer of the lowersubstrate, a region corresponding to the spacer of the alignment filmmay be attached to the pressure-sensitive adhesive layer of the uppersubstrate.

The pressure-sensitive adhesive layer may have a storage elastic modulusof 1 MPa or less. The lower limit of the storage elastic modulus of thepressure-sensitive adhesive layer may be, for example, 0.01 MPa or more.Specifically, the storage elastic modulus (G2) of the pressure-sensitiveadhesive layer may be 0.02 MPa or more, 0.04 MPa, 0.06 MPa, 0.08 MPa or0.1 MPa or more, and may be 0.8 MPa or less, 0.6 MPa or less, 0.4 MPa orless, or 0.2 MPa or less. The storage elastic modulus may be a valuemeasured at a temperature of 25° C. and a frequency of 6 rad/sec. Inorder to overcome the physical limits of the liquid crystal element, theouter substrates can be bonded together via the intermediate layers onboth sides of the liquid crystal element, but due to the low modulus ofthe pressure-sensitive adhesive layer, it is vulnerable to an externalpressure, whereby defects such as cell gap collapse or liquid crystalflow or crowding may occur. According to the present disclosure, asdescribed below, the thicknesses of the intermediate layers included inthe optical device are controlled, whereby the defects can be minimizedand the structural stability and quality uniformity of the opticaldevice can be secured.

The liquid crystal layer may comprise a liquid crystal compound. As theliquid crystal compound, a liquid crystal compound, the orientationdirection of which may be changed by application of an external action,may be used. In this specification, the term “external action” may meanany external factor that may affect the behavior of a material includedin the liquid crystal layer, for example, an external voltage or thelike. Therefore, the state where there is no external action may mean astate where there is no application of an external voltage or the like.

The type and physical properties of the liquid crystal compound may beappropriately selected in consideration of the purpose of the presentdisclosure. In one example, the liquid crystal compound may be a nematicliquid crystal or a smectic liquid crystal. The nematic liquid crystalmay mean a liquid crystal that rod-shaped liquid crystal molecules arearranged in parallel in the long-axis direction of the liquid crystalmolecules although there is no regularity in their positions. Thesmectic liquid crystal may mean a liquid crystal that rod-shaped liquidcrystal molecules are regularly arranged to form a layered structure andare arranged in parallel with regularity in the long axis direction.According to one example of the present disclosure, the liquid crystalcompound may be a nematic liquid crystal compound.

As the nematic liquid crystal compound, one having a clearing point of,for example, about 40° C. or more, about 50° C. or more, about 60° C. ormore, about 70° C. or more, about 80° C. or more, about 90° C. or more,about 100° C. or more, or about 110° C. or more, or having a phasetransition point in the above range, that is, a phase transition pointto an isotropic phase from a nematic phase, can be selected. In oneexample, the clearing point or phase transition point may be about 160°C. or less, about 150° C. or less, or about 140° C. or less.

The liquid crystal compound may be a non-reactive liquid crystalcompound. The non-reactive liquid crystal compound may mean a liquidcrystal compound having no polymerizable group. The polymerizable groupmay be exemplified by an acryloyl group, an acryloyloxy group, amethacryloyl group, a methacryloyloxy group, a carboxyl group, a hydroxygroup, a vinyl group or an epoxy group, and the like, but is not limitedthereto, and a functional group known as the polymerizable group may beincluded.

The liquid crystal compound may have dielectric constant anisotropy of apositive number or a negative number. The absolute value of thedielectric constant anisotropy of the liquid crystal compound may beappropriately selected in consideration of the purpose of the presentdisclosure. The term “dielectric constant anisotropy (Δε)” may mean adifference (ε//−ε⊥) between the horizontal dielectric constant (ε//) andthe vertical dielectric constant (ε⊥) of the liquid crystal. In thisspecification, the term horizontal dielectric constant (ε//) means adielectric constant value measured along the direction of an electricfield in a state where a voltage is applied so that the director of theliquid crystal and the direction of the electric field by the appliedvoltage are substantially horizontal, and the vertical dielectricconstant (ε⊥) means a dielectric constant value measured along thedirection of an electric field in a state where a voltage is applied sothat the director of the liquid crystal and the direction of theelectric field by the applied voltage are substantially perpendicular.The dielectric constant anisotropy of the liquid crystal molecules maybe in a range of 5 to 25.

The refractive index anisotropy of the liquid crystal compound may beappropriately selected in consideration of the purpose of the presentdisclosure. In this specification, the term “refractive indexanisotropy” may mean a difference between an extraordinary refractiveindex and an ordinary refractive index of a liquid crystal compound. Therefractive index anisotropy of the liquid crystal compound may be, forexample, 0.01 to 0.3. The refractive index anisotropy may be 0.01 ormore, 0.05 or more, or 0.07 or more, and may be 0.3 or less, 0.2 orless, 0.15 or less, or 0.13 or less.

The liquid crystal layer may further comprise a dichroic dye. When theliquid crystal layer comprises a dichroic dye, the cell gap fluctuationis less affected upon a lamination process of outer substrates even ifthe liquid crystal element comprises a pressure-sensitive adhesivelayer, so that there is an advantage that the thickness of theintermediate layers can be made relatively thin for securing structuralstability and quality uniformity of the liquid crystal element.

The dichroic dye may control light transmittance variable properties ofthe liquid crystal layer. In this specification, the term “dye” may meana material capable of intensively absorbing and/or deforming light in atleast a part or all of the ranges within a visible light region, forexample, within a wavelength range of 400 nm to 700 nm, and the term“dichroic dye” may mean a material capable of anisotropic absorption oflight in at least a part or all of the ranges of the visible lightregion.

The liquid crystal layer comprising the liquid crystal compound and thedichroic dye may be a GHLC layer (guest host liquid crystal layer). Inthis specification, the “GHLC layer (guest host liquid crystal layer)”may mean a functional layer that dichroic dyes are arranged togetherdepending on arrangement of the liquid crystal compound to exhibitanisotropic light absorption characteristics with respect to analignment direction of the dichroic dyes and the direction perpendicularto the alignment direction, respectively. For example, the dichroic dyeis a substance whose absorption rate of light varies with a polarizationdirection, where if the absorption rate of light polarized in the longaxis direction is large, it may be referred to as a p-type dye, and ifthe absorption rate of polarized light in the short axis direction islarge, it may be referred to as an n-type dye. In one example, when ap-type dye is used, the polarized light vibrating in the long axisdirection of the dye may be absorbed and the polarized light vibratingin the short axis direction of the dye may be less absorbed to betransmitted. Hereinafter, unless otherwise specified, the dichroic dyeis assumed to be a p-type dye.

As the dichroic dye, for example, a known dye known to have a propertycapable of being aligned according to the orientation state of theliquid crystal compound by a so-called guest host effect may be selectedand used. An example of such a dichroic dye includes azo dyes,anthraquinone dyes, methine dyes, azomethine dyes, merocyanine dyes,naphthoquinone dyes, tetrazine dyes, phenylene dyes, quarterrylene dyes,benzothiadiazole dyes, diketopyrrolopyrrole dyes, squaraine dyes orpyromethene dyes, and the like, but the dyes applicable in the presentdisclosure are not limited thereto.

As the dichroic dye, a dye having a dichroic ratio, that is, a valueobtained by dividing the absorption of the polarized light parallel tothe long axis direction of the dichroic dye by the absorption of thepolarized light parallel to the direction perpendicular to the long axisdirection, of 5 or more, 6 or more, or 7 or more, can be used. The dyemay satisfy the dichroic ratio in at least a part of the wavelengths orany one wavelength within the wavelength range of the visible lightregion, for example, within the wavelength range of about 380 nm to 700nm or about 400 nm to 700 nm. The upper limit of the dichroic ratio maybe, for example, 20 or less, 18 or less, 16 or less, or 14 or less orso.

The content of the dichroic dye in the liquid crystal layer may beappropriately selected in consideration of the purpose of the presentdisclosure. For example, the content of the dichroic dye in the liquidcrystal layer may be 0.2 wt % or more. The content of the dichroic dyemay specifically be 0.5 wt % or more, 1 wt % or more, 2 wt % or more, or3 wt % or more. The upper limit of the content of the dichroic dye maybe, for example, 10 wt % or less, 9 wt % or less, 8 wt % or less, 6 wt %or less, or 5 wt % or less. When the content of the dichroic dye in theliquid crystal layer is too small, it may be difficult to express thedesired transmittance variable characteristics, and it may beinsufficient to reduce the thickness of the intermediate layer forreducing cell gap fluctuations that may occur upon lamination process ofthe outer substrates. Meanwhile, when the content of the dichroic dye inthe liquid crystal layer is too large, there is a risk of precipitation.Therefore, it may be advantageous that the content of the dichroic dyeis within the above range.

The thickness of the liquid crystal layer is not particularly limited,and for example, the thickness of the liquid crystal layer may be about0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.5 μm or more, 1 μmor more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, 3.5μm or more, 4 μm or more, 4.5 μm or more, 5 μm or more, 5.5 μm or more,6 μm or more, 6.5 μm or more, 7 μm or more, 7.5 μm or more, 8 μm ormore, 8.5 μm or more, 9 μm or more, or 9.5 μm or more. The upper limitof the thickness of the liquid crystal layer is not particularlylimited, which may generally be about 30 μm or less, 25 μm or less, 20μm or less, or 15 μm or less.

The liquid crystal layer may switch between a first orientation stateand a second orientation state different from the first orientationstate. The switching may be adjusted, for example, through theapplication of external energy such as a voltage. For example, theliquid crystal layer may maintain any one of the first and secondorientation states in a state where no voltage is applied, and may beswitched to the other orientation state by voltage application.

In one example, the first orientation state may be a twist orientationstate. That is, the liquid crystal layer may switch between twistorientation and an orientation state different from the twistorientation through the application of external energy. In this case,the optical device may not comprise a polarizer between the first outersubstrate and the liquid crystal element and between the second outersubstrate and the liquid crystal element. In one example, the liquidcrystal layer may switch between the twist orientation and verticalorientation states. In one example, the liquid crystal layer may be inthe twist orientation state in a state where no voltage is applied, andmay be in the vertical orientation state in a state where a voltage isapplied.

In this specification, the “vertical orientation state” is a state wheredirectors of a liquid crystal compound in a liquid crystal layer arearranged approximately perpendicular to the plane of the liquid crystallayer, where for example, the angle formed by the director of the liquidcrystal compound with respect to the plane of the liquid crystal layermay be, for example, in a range of about 80 degrees to 100 degrees or 85degrees to 95 degrees, or it may form approximately about 90 degrees.

In this specification, the “twist orientation state” may mean a spiralstructure in which directors of a liquid crystal compound in a liquidcrystal layer form layers while twisting along an imaginary spiral axisand oriented. The twist orientation state may be implemented in avertical, horizontal or oblique orientation state. That is, the verticaltwist orientation mode is a state where individual liquid crystalcompounds form layers while twisting along the spiral axis in avertically oriented state; the horizontal twist orientation mode is astate where individual liquid crystal compounds form layers whiletwisting along the spiral axis in a horizontally oriented state; and theoblique twist orientation mode is a state where individual liquidcrystal compounds form layers while twisting along the spiral axis in anobliquely oriented state. According to the present disclosure, the twistorientation state may be a twist orientation state of the horizontalorientation state.

In the twist orientation state, the ratio (d/p) of the thickness (d) tothe pitch (p) of the liquid crystal layer may be 20 or less, and thelower limit may be 0.5 or more. When the ratio (d/p) of the thickness(d) to the pitch (p) in the twist orientation state is within the aboverange, the optical device may exhibit excellent light transmittancevariable characteristics even in a state without any polarizer. Ingeneral, when the ratio d/p is 0.7 or more and less than 2.5, it may becalled an STN (super twisted nematic) mode, and when the ratio d/p is2.5 or more, it may be called an HTN (highly twisted nematic) drivingmode.

The pitch (p) of the liquid crystal layer can be measured by ameasurement method using a wedge cell, and specifically, can be measuredby a method described in D. Podolskyy et al. Simple method for accuratemeasurements of the cholesteric pitch using a “stripe-wedgeGrandjean-Cano cell (Liquid Crystals, Vol. 35, No. 7, July 2008,789-791). The ratio (d/p) can be achieved by introducing an appropriateamount of a chiral dopant into the liquid crystal layer.

The liquid crystal layer may further comprise a chiral dopant, When theliquid crystal layer comprises a chiral agent, the twist orientationstate may be implemented. The chiral agent (or chiral dopant) that canbe included in the liquid crystal layer can be used without particularlimitation as long as it can induce a desired rotation (twisting)without deteriorating the liquid crystallinity, for example, the nematicregularity. The chiral agent for inducing rotation in the liquid crystalcompound needs to include at least chirality in the molecular structure.The chiral agent may be exemplified by, for example, a compound havingone or two or more asymmetric carbons, a compound having an asymmetricpoint on a heteroatom, such as a chiral amine or a chiral sulfoxide, ora compound having axially asymmetric and optically active sites such ascumulene or binaphthol. The chiral agent may be, for example, a lowmolecular weight compound having a molecular weight of 1,500 or less. Asthe chiral agent, commercially available chiral nematic liquid crystals,for example, chiral dopant liquid crystal S811 commercially availablefrom Merck Co., Ltd. or BASF's LC756 may also be used.

The application ratio of the chiral dopant is selected so that thedesired ratio (d/p) can be achieved. In general, the content (wt %) ofthe chiral dopant may be calculated by an equation of 100/HTP (helicaltwisting power)×pitch (p)(nm). The HTP represents the strength of thetwist of the chiral dopant, where the content of the chiral dopant maybe determined in consideration of the desired pitch with reference tothe above method.

In another example, the first orientation state may be a horizontalorientation state. That is, the liquid crystal layer may switch betweenhorizontal orientation and an orientation state different from thehorizontal orientation through external energy application. In oneexample, the liquid crystal layer may switch between a horizontalalignment and a vertical orientation state. In one example, the liquidcrystal layer may be in a horizontal orientation state in a state whereno voltage is applied, and may be in a vertical orientation state in astate where a voltage is applied. In this case, the optical device mayfurther comprise one polarizer between the first outer substrate and theliquid crystal element or between the second outer substrate and theliquid crystal element.

In this specification, the “horizontal orientation state” is a statewhere directors of a liquid crystal compound in a liquid crystal layerare arranged approximately parallel to the plane of the liquid crystallayer, where for example, the angle formed by the director of the liquidcrystal compound with respect to the plane of the liquid crystal layermay be, for example, in a range of about 0 degrees to 10 degrees or 0degrees to 5 degrees, or it may form approximately about 0 degrees.

The liquid crystal element may further comprise a first electrode layer(10 b) formed on the inner surface of the first base layer (10 a). Atthis time, the pressure-sensitive adhesive layer (10 c) may be presenton the inner surface of the first electrode layer (10 b). That is, thefirst electrode layer (10 b) may exist between the first base layer (10a) and the pressure-sensitive adhesive layer (10 c). The liquid crystalelement may further comprise a second electrode layer (20 b) formed onthe inner surface of the second base layer (20 a). At this time, thespacer (20 c) may be present on the inner surface of the secondelectrode layer (20 b). That is, the second electrode layer (20 b) mayexist between the second base layer (20 a) and the spacer (20 c).

The first electrode layer and the second electrode layer may serve toprovide application of an external action, for example, an electricfield, so that the material included in the liquid crystal layertransmits or blocks incident light. In one example, the first electrodelayer and/or the second electrode layer may comprise a conductivepolymer, a conductive metal, a conductive nanowire or a metal oxide suchas ITO (indium tin oxide), and the like, but is not limited thereto. Theupper and/or lower second electrode layer may be formed by, for example,depositing the conductive polymer, the conductive metal, the conductivenanowire or the metal oxide such as ITO (indium tin oxide).

The liquid crystal element may further comprise an alignment film (20 d)on the inner surface of the second electrode layer (20 b). The spacer(20 c) may exist between the second electrode layer (20 b) and thealignment film (20 d). The alignment film may be formed on the spacer.That is, the top surface portion and/or the side surface portions of thespacer may be in contact with the alignment film. The bottom surface ofthe spacer may contact the second electrode layer. Since thepressure-sensitive adhesive layer may have liquid crystal orientationproperties, the alignment film may not be included on the inner surfaceof the first electrode layer.

In this specification, the combination of the first base layer, thefirst electrode layer and the pressure-sensitive adhesive layer may bereferred to as the upper substrate, and the combination of the secondbase layer, the second electrode layer, the spacer and the alignmentfilm may be referred to as the lower substrate. In the liquid crystalelement, the upper substrate may not comprise a separate alignment filmother than the pressure-sensitive adhesive layer, and the lowersubstrate may comprise the alignment film.

The alignment film and the liquid crystal layer may be in contact witheach other. The alignment film may be a vertical alignment film or ahorizontal alignment film. In this specification, the “horizontalalignment film” may mean a layer comprising an orientational materialthat imparts horizontal orientation force to a liquid crystal compoundpresent in an adjacent liquid crystal layer. In this specification, the“vertical alignment film” may mean a layer comprising an orientationalmaterial that imparts vertical orientation force to a liquid crystalcompound present in an adjacent liquid crystal layer. The adjacentliquid crystal compound may have a pretilt angle with respect to thevertical alignment film in the range of 80 degrees to 90 degrees, 85degrees to 90 degrees, or about 87 degrees to 90 degrees, and theadjacent liquid crystal compound may have a pretilt angle with respectto the horizontal alignment film in the range of 0 degrees to 10degrees, 0 degrees to 5 degrees or 0 degrees to 3 degrees. Unlike thepressure-sensitive adhesive layer, the alignment film may not haveadhesive force for bonding the upper substrate and the lower substrate.In one example, the alignment film may have peel force close to zerowith regard to the first base layer in the state of the liquid crystalelement of FIG. 2 .

The alignment film may be a rubbing alignment film or a photo-alignmentfilm. The orientation direction of the alignment film may be a rubbingdirection in the case of a rubbing alignment film and a direction ofpolarized light to be irradiated in the case of a photo-alignment film,where such an orientation direction can be confirmed by a detectionmethod using an absorption-type linear polarizer. Specifically, theorientation direction can be confirmed by disposing an absorption-typelinear polarizer on one side of the liquid crystal layer in a statewhere the liquid crystal compound included in the liquid crystal layeris horizontally oriented, and measuring transmittance while rotating thepolarizer at 360 degrees. When the side of the liquid crystal layer orthe absorption-type linear polarizer is irradiated with light in theabove state and simultaneously the luminance (transmittance) is measuredfrom the other side, the transmittance tends to be low, if theabsorption axis or transmission axis coincides with the orientationdirection of the liquid crystal alignment film, where the orientationdirection can be confirmed through simulation reflecting the refractiveindex anisotropy of the applied liquid crystal compound or the like. Amethod of confirming the orientation direction according to the mode ofthe liquid crystal layer is known, and in the present disclosure, theorientation direction of the alignment film can be confirmed by such aknown method.

The alignment film may comprise one or more selected from the groupconsisting of a material known to exhibit orientation ability by rubbingorientation such as a polyimide compound, a poly(vinyl alcohol)compound, a poly(amic acid) compound, a polystyrene compound, apolyamide compound and a polyoxyethylene compound, or a material knownto exhibit orientation ability by light irradiation such as a polyimidecompound, a polyamic acid compound, a polynorbornene compound, aphenylmaleimide copolymer compound, a polyvinylcinnamate compound, apolyazobenzene compound, a polyethyleneimide compound, apolyvinylalcohol compound, a polyamide compound, a polyethylenecompound, a polystyrene compound, a polyphenylenephthalamide compound, apolyester compound, a CMPI (chloromethylated polyimide) compound, a PVCI(polyvinylcinnamate) compound and a polymethyl methacrylate compound,but is not limited thereto.

The spacer (20 c) may maintain the gap between the upper substrate andthe lower substrate. The liquid crystal layer may be present in a regionwhere the spacer does not exist between the upper substrate and thelower substrate.

The spacer may be a patterned spacer. The spacer may have a column shapeor a partition wall shape. The partition wall may partition the spacebetween the lower substrate and the upper substrate into two or morespaces. In the region where the spacer does not exist, other films orother layers present in the lower part may be exposed. For example, thesecond electrode layer may be exposed in a region where the spacer doesnot exist. The alignment film may cover the spacer and the secondelectrode layer exposed in the region where the spacer is not present.In the liquid crystal element in which the upper substrate and the lowersubstrate are bonded together, the alignment film present on the spacerof the lower substrate and the pressure-sensitive adhesive layer of theupper substrate may be in contact with each other.

The liquid crystal compound and the above-described additives, forexample, the dichroic dye, the chiral agent, and the like may be presentin the region between the upper substrate and the lower substrate wherethe spacer does not exist. The shape of the spacer is not particularlylimited, which can be applied without limitation so as to have, forexample, a circle, an ellipse, or other polygonal-shaped polyhedrons.

The spacer may comprise a curable resin. The type of the curable resinis not particularly limited, where for example, a thermosetting resin ora photo-curable resin, for example, an ultraviolet curable resin may beused. As the thermosetting resin, for example, a silicone resin, asilicon resin, a furan resin, a polyurethane resin, an epoxy resin, anamino resin, a phenol resin, a urea resin, a polyester resin or amelamine resin, and the like may be used, without being limited thereto.As the ultraviolet curable resin, typically an acrylic polymer, forexample, a polyester acrylate polymer, a polystyrene acrylate polymer,an epoxy acrylate polymer, a polyurethane acrylate polymer or apolybutadiene acrylate polymer, a silicone acrylate polymer or an alkylacrylate polymer, and the like may be used, without being limitedthereto.

The spacer may be formed by a patterning process. For example, thespacer may be formed by a photolithography process. The photolithographyprocess may comprise a process of applying a curable resin compositionon a base layer or an electrode layer and then irradiating it withultraviolet rays via a pattern mask. The pattern mask may be patternedinto an ultraviolet transmitting region and an ultraviolet blockingregion. The photolithography process may further comprise a process ofwashing the curable resin composition irradiated with ultraviolet rays.The region irradiated with ultraviolet rays is cured, and the regionirradiated with no ultraviolet rays remains in a liquid phase, so thatit is removed through the washing process, whereby it can be patternedinto a partition wall shape. In the photolithography process, a releasetreatment may be performed on the pattern mask in order to easilyseparate the resin composition and the pattern mask after ultravioletirradiation, or a release paper may also be placed between the layer ofthe resin composition and the pattern mask.

The width (line width), spacing (pitch), thickness and area of thespacer may be appropriately selected within a range without impairingthe purpose of the present disclosure. For example, the width (linewidth) of the spacer may be in a range of 10 μm to 500 μm or in a rangeof 10 μm to 50 μm. The spacing (pitch) of the spacer may be in a rangeof 10 μm to 1000 μm or in a range of 100 μm to 1000 μm. The area of thespacer may be about 5% or more and may be 50% or less, relative to 100%of the total area of the second base layer. When the area of the spaceris within the above range, it may be advantageous to ensure excellentelectro-optical properties while adequately securing attachment forcebetween the upper substrate and the lower substrate. The thickness ofthe spacer may range, for example, from 1 μm to 30 μm or from 3 μm to 20μm.

The optical device may comprise at least one or more intermediate layerspositioned between the first outer substrate and the liquid crystalelement, and may comprise at least one or more intermediate layerspositioned between the second outer substrate and the liquid crystalelement. Therefore, the optical device may comprise at least twointermediate layers. One side of each of the first outer substrate andthe second outer substrate may be in contact with the adjacentintermediate layer. Both sides of the liquid crystal element may be incontact with adjacent intermediate layers, respectively.

The number of intermediate layers of the optical device may bedetermined according to whether the optical device further comprisesother elements in addition to the first outer substrate, the secondouter substrate and the liquid crystal element. The other element may beexemplified by a polarizer or the like.

In one example, the optical device may further comprise other elements,for example, a polarizer, in addition to the liquid crystal element,between the first outer substrate and the second outer substrate. Inthis case, as one embodiment, the optical device may have a structure inwhich a first outer substrate, an intermediate layer, a liquid crystalelement, an intermediate layer, a polarizer, an intermediate layer and asecond outer substrate are laminated in this order. In anotherembodiment, the optical device may have a structure in which a firstouter substrate, an intermediate layer, a polarizer, an intermediatelayer, a liquid crystal element, an intermediate layer and a secondouter substrate are laminated in this order. As another example, theoptical device may have a structure in which a first outer substrate, anintermediate layer, a polarizer, an intermediate layer, a liquid crystalelement, an intermediate layer, a polarizer, an intermediate layer and asecond outer substrate are laminated in this order.

In another example, the optical device may not comprise other elements,for example, a polarizer, in addition to the liquid crystal element,between the first outer substrate and the second outer substrate. Inthis case, the optical device may have a structure in which the firstouter substrate, the intermediate layer, the liquid crystal element, theintermediate layer and the second outer substrate are laminated in thisorder.

In order to overcome the physical limits of the liquid crystal element,the outer substrates can be bonded together via the intermediate layerson both sides of the liquid crystal element, but due to the low modulusof the pressure-sensitive adhesive layer, it is vulnerable to anexternal pressure, whereby defects such as cell gap collapse or liquidcrystal flow or crowding may occur. The thicknesses of the intermediatelayers included in the optical device are controlled, whereby thedefects can be minimized and the structural stability and qualityuniformity of the optical device can be secured.

As one example, the sum of the total thicknesses of the at least one ormore intermediate layers may be 800 μm or more. The sum of the totalthicknesses of the at least one or more intermediate layers means thesum of the thicknesses of all intermediate layers existing between thefirst outer substrate and the liquid crystal element and between thesecond outer substrate and the liquid crystal element. When the totalthickness of the intermediate layers is within the above range, it ispossible to secure structural stability and uniform appearancecharacteristics of the optical device by minimizing defects in thelamination process of the outer substrate. Specifically, the sum of thetotal thicknesses of the at least one or more intermediate layers may be900 μm or more, 1,000 μm or more, 1,100 μm or more, 1200 μm or more,1,300 μm or more, 1,400 μm or more, 1,500 μm or more, 1,600 μm or more,about 1,650 μm or more, 1,700 μm or more, 1,750 μm or more, 1,800 μm ormore, 1,850 μm or more, 1,900 μm or more, 1,950 μm or more, 2,000 μm ormore, 2,100 μm or more, 2,150 μm or more, or about 2,200 μm or more. Thesum of the total thicknesses of the at least one or more intermediatelayers may be, for example, about 6,000 μm or less, 5,900 μm or less,5,800 μm or less, 5,700 μm or less, 5,600 μm or less, 5,500 μm or less,5,400 μm or less, 5,300 μm or less, 5,200 μm or less, 5,100 μm or less,or about 5,000 μm or less. When the sum of the total thicknesses of theat least one or more intermediate layers is too thick, electro-opticalproperties such as transmittance properties of the optical device may bedeteriorated, so that it may be advantageous to be within the aboverange.

The at least one or more intermediate layers may each have asingle-layer structure of one intermediate layer or may be a laminate oftwo or more sub-intermediate layers. The thickness and number ofsub-intermediate layers may be controlled in consideration of thedesired thickness of the intermediate layer. In one example, thethickness of the sub-intermediate layer may be in the range of 100 μm to500 μm or in the range of 300 μm to 400 μm.

As an example, the total thicknesses (Ta) of the at least one or moreintermediate layers positioned between the first outer substrate and theliquid crystal element and the total thicknesses (Tb) of the at leastone or more intermediate layers positioned between the second outersubstrate and the liquid crystal element may each be about 400 μm ormore, 500 μm or more, 600 μm or more, 700 μm or more, 800 μm or more,900 μm or more, 1000 μm or more, or 1100 μm or more, and may be about3,000 μm or less, 2,900 μm or less, 2,800 μm or less, 2,700 μm or less,about 2,600 μm or less, about 2,500 μm or less, about 2,400 μm or less,or about 2,300 μm or less. When the thicknesses Ta and Tb are within theabove ranges, it may be advantageous to secure structural stability anduniform appearance characteristics without defects in the laminationprocess of the outer substrates, without impairing the electro-opticalproperties of the optical device. The sum of the total thicknesses (Ta)of the at least one or more intermediate layers positioned between thefirst outer substrate and the liquid crystal element means the sum ofthe thicknesses of all intermediate layers existing between the firstouter substrate and the liquid crystal element. In addition, the sum ofthe total thicknesses (Tb) of the at least one intermediate layerpositioned between the second outer substrate and the liquid crystalelement means the sum of the thicknesses of all intermediate layerspresent between the second outer substrate and the liquid crystalelement.

As one example, the thickness ratio (Ta/Tb) of the total thicknesses(Ta) of the at least one or more intermediate layers (200 a) positionedbetween the first outer substrate (100 a) and the liquid crystal element(300) to the total thicknesses (Tb) of the at least one or moreintermediate layers (200 b) positioned between the second outersubstrate (100 b) and the liquid crystal element (300) may be in therange of 0.1 to 10. As another example, the thickness ratio (Ta/Tb) maybe about 0.12 or more, about 0.13 or more, or about 0.14 or more, andmay be about 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 orless, or about 7.0 or less. When the thickness ratio is within the rangeof 0.1 to 10, it is possible to more effectively improve the appearancedefects of the liquid crystal element.

As one example, the storage elastic moduli of the at least one or moreintermediate layers may each be 1 MPa or more. When the storage elasticmoduli of the intermediate layers are low, the liquid crystal elementmay also be damaged because the base layer cannot withstand the stressof contraction and expansion in a high temperature durability test or acycle test, and the like. The storage elastic modulus of theintermediate layer may be 2 MPa or more, or 4 MPa or more, and may be100 MPa or less, 80 MPa or less, 60 MPa or less, 40 MPa or less, 20 MPaor less, 10 MPa or less, or 5 MPa or less. The storage elastic modulusmay be a value measured at a temperature of 25° C. and a frequency of 6rad/sec.

As one example, the at least one or more intermediate layers may eachhave a Young's modulus (E) in a range of 0.1 MPa to 100 MPa. As anotherexample, the Young's modulus (E) of the intermediate layer may be about0.2 MPa or more, 0.4 MPa or more, 0.6 MPa or more, MPa or more, 1 MPa ormore, 5 MPa or more, or about 10 MPa or more, and may be about MPa orless, 80 MPa or less, 75 MPa or less, 70 MPa or less, 65 MPa or less, 60MPa or less, 55 MPa or less, or about 50 MPa or less. The Young'smodulus (E), for example, can be measured in the manner specified inASTM D882, and can be measured using the equipment that can cut the filmin the form provided by the relevant standard and measure thestress-strain curve (can measure the force and length simultaneously),for example, a UTM (universal testing machine). When the Young's moduliof the intermediate layers included in the optical device are within theabove range, it may be more advantageous to ensure excellent durabilityof the optical device. When the intermediate layer is a laminate of atleast two or more sub-intermediate layers, each of the sub-intermediatelayers may satisfy the above Young's modulus range.

As one example, the at least one or more intermediate layers may eachhave a coefficient of thermal expansion of 2,000 ppm/K or less. Inanother example, the coefficient of thermal expansion may be about 1,900ppm/K or less, 1,700 ppm/K or less, 1,600 ppm/K or less, or about 1.500ppm/K or less, or may be about 10 ppm/K or more, 20 ppm/K or more, 30ppm/K or more, 40 ppm/K or more, 50 ppm/K or more, 60 ppm/K or more, 70ppm/K or more, ppm/K or more, 90 ppm/K or more, 100 ppm/K or more, 200ppm/K or more, 300 ppm/K or more, 400 ppm/K or more, 500 ppm/K or more,60 ppm/K or more, 700 ppm/K or more, or about 800 ppm/K or more. Thecoefficient of thermal expansion of the intermediate layer can bemeasured, for example, according to the regulations of ASTM D696, wherethe coefficient of thermal expansion can be calculated by cutting it inthe form provided by the relevant standard, and measuring the change inlength per unit temperature, and can be measured by a known method suchas the TMA (thermo-mechanic analysis). When the coefficients of thermalexpansion of the intermediate layers included in the optical device arewithin the above range, it may be more advantageous to ensure excellentdurability of the optical device. When the intermediate layer is alaminate of at least two or more sub-intermediate layers, each of thesub-intermediate layers may satisfy the range of the coefficient ofthermal expansion.

The at least one or more intermediate layers may each be a thermoplasticpolyurethane (TPU) adhesive layer, a polyamide adhesive layer, apolyester adhesive layer, an EVA (ethylene vinyl acetate) adhesivelayer, an acrylic adhesive layer, a silicone adhesive layer or apolyolefin adhesive layer. According to one example of the presentdisclosure, the at least one or more intermediate layers may each be athermoplastic polyurethane.

The optical device may further comprise an outer layer surrounding thesides of the liquid crystal element. In the optical device, the top areaof the liquid crystal element may be smaller than the top area of thefirst outer substrate or the second outer substrate. Also, the top areaof the liquid crystal element may be smaller than the top areas of atleast one or more intermediate layers included in the optical device. Inone example, the liquid crystal element may be encapsulated by anintermediate layer positioned between the first outer substrate and theliquid crystal element, an intermediate layer positioned between thesecond outer substrate and the liquid crystal element, and the outerlayer. In the present disclosure, the term encapsulation may meancovering the entire surface of the liquid crystal element with theintermediate layers and the outer layer. Depending on the desiredstructure, for example, the encapsulation structure may be implementedby a method of compressing a laminate comprising a first outersubstrate, an intermediate layer, a liquid crystal element, anintermediate layer and a second outer substrate sequentially andcomprising an outer layer surrounding the sides of the liquid crystalelement in a vacuum state. The durability and weather resistance of theoptical device are greatly improved by such an encapsulation structure,and as a result, it can be stably applied to outdoor applications suchas a sunroof.

The outer layer may comprise, for example, a thermoplastic polyurethane(TPU) adhesive, a polyamide adhesive, a polyester adhesive, an EVA(ethylene vinyl acetate) adhesive, an acrylic adhesive, a siliconeadhesive or a polyolefin adhesive. In one example, the outer layer maybe formed of the same material as that of the intermediate layer.

The present disclosure also relates to a method for manufacturing anoptical device. The manufacturing method of the optical device maycomprise steps of preparing a laminate sequentially comprising a firstouter substrate, at least one or more intermediate layers, a liquidcrystal element, at least one or more intermediate layers and a secondouter substrate, and autoclaving the laminate. Unless otherwisespecified in the manufacturing method of the optical device, thecontents described in the optical device may be equally applied.

The laminate may further comprise an outer layer surrounding the sidesof the liquid crystal element.

When the optical device further comprises other elements, for example, apolarizer, in addition to the liquid crystal element, the laminate mayfurther comprise other elements at a desired position, in addition tothe liquid crystal element.

The autoclave process may be performed by heating and/or pressing thelaminate formed after the laminating step.

The conditions of the autoclave process are not particularly limited,and it may be performed under an appropriate temperature and pressure,for example, depending on the type of the applied intermediate layers.The temperature of a typical autoclave process is about 80° C. or more,90° C. or more, 100° C. or more, and the pressure is 2 atmospheres ormore, without being limited thereto. The upper limit of the processtemperature may be about 200° C. or less, 190° C. or less, 180° C. orless, or 170° C. or less or so, and the upper limit of the processpressure may be about 10 atm or less, 9 atm or less, 8 atm or less, 7atm or less, or 6 atm or less or so.

Such an optical device can be used for various applications, and forexample, can be used for eyewear such as sunglasses or AR (augmentedreality) or VR (virtual reality) eyewear, an outer wall of a building ora sunroof for a vehicle, and the like. In one example, the opticaldevice itself may be a sunroof for a vehicle. For example, in anautomobile including an auto body in which at least one opening isformed, the optical device or the sunroof for a vehicle attached to theopening can be mounted and used.

Effects of Invention

The optical device of the present disclosure can ensure structuralstability and good quality uniformity by maintaining the cell gap of theliquid crystal element properly, having excellent attachment forcebetween the upper substrate and the lower substrate, and minimizingdefects such as pressing or crowding in the lamination process of theouter substrates.

Mode for Invention

Hereinafter, the present disclosure will be described in detail throughExamples, but the scope of the present disclosure is not limited byExamples below.

Measurement Example 1. Measurement of Storage Elastic Modulus

The storage elastic modulus was measured using TA's DMA Q800.Specifically, the storage elastic modulus value was recorded under theconditions of a temperature of 25 ° C., a frequency of 6 rad/sec, aforce of 0.01N, and a ramp rate of 3°/min in the Multi-Frequency-StrainStrain mode.

Example 1 Liquid Crystal Element Manufacturing

A polycarbonate film (Keiwa) having a thickness of about 100 μm and awidth x height area of 900 mm×600 mm was prepared as a first base layer.ITO (indium-tin-oxide) was deposited on the first base layer to athickness of 50 nm to form a first electrode layer. A pressure-sensitiveadhesive composition (KR-3700, Shin-Etsu) was bar-coated on the firstelectrode layer, and then dried at about 150° C. for about 5 minutes toform a pressure-sensitive adhesive layer having a thickness of about 10μm. The storage modulus of the adhesive layer was about 0.1 MPa. Thecombination of the first base layer, the first electrode layer and thepressure-sensitive adhesive layer is referred to as an upper substrate.

As a second base layer, a polycarbonate film (Keiwa) having a thicknessof about 100 μm and a width×height area of 900 mm×600 mm was prepared.On the second base layer, ITO (indium-tin-oxide) was deposited to athickness of 50 nm to form a second electrode layer. An acrylic resincomposition (KAD-03, Minuta Tech) was coated on the second electrodelayer, and then a honeycomb-type spacer (partition wall spacer) wasformed by a photolithography method. The pitch of the regular hexagons(closed figure) constituting the honeycomb is about 450 μm, the heightis about 12 μm, and the line width is about 30 μm. The area of theclosed figure (regular hexagon) formed by the spacer was approximately2.14 mm 2 . A horizontal alignment film (Nissan, SE-7492K) was coated onthe spacer to a thickness of about 300 nm, and then rubbed in onedirection. The combination of the second base layer, the secondelectrode layer, the spacer, and the horizontal alignment film isreferred to as a lower substrate.

A liquid crystal composition was coated on the horizontal alignment filmof the lower substrate to form a liquid crystal layer, and then thepressure-sensitive adhesive layer of the upper substrate was laminatedto face the coated surface of the liquid crystal composition. The liquidcrystal composition comprises a liquid crystal compound (JNC,SHN-5011XX), a chiral dopant (HCCH, S811) and a dichroic dye (LG Chem,black dye combination), where the content of the chiral dopant in theliquid crystal composition is 3.7 wt % and the content of the dichroicdye is 3 wt %. The pitch (p) of the liquid crystal layer thus formed wasabout 2.5 μm, and the ratio (d/p) of the cell gap (d) to the pitch (p)was about 4.8. The liquid crystal element is an HTN mode liquid crystalcell having a twist angle of 1720 degrees when no voltage is applied.

Optical Device Manufacturing

A laminate comprising a first outer substrate, a first intermediatelayer, the prepared liquid crystal element, a second intermediate layerand a second outer substrate sequentially and comprising an outer layersurrounding the sides of the liquid crystal element was prepared.Compared to the first outer substrate, the second outer substrate wasdisposed in the direction of gravity.

As the first outer substrate, a glass substrate having a thickness ofabout 3 mm, an area of width×length=1100 mm×800 mm and a curvatureradius of about 2,470 R was used. As the second outer substrate, a glasssubstrate having a thickness of about 3 mm, an area of width×length=300mm×300 mm and a curvature radius of about 2,400 R was used. The firstintermediate layer and the second intermediate layer are each a laminateof two TPU layers (Argotec), one layer of which has a thickness of about380 μm. The TPU layer (Argotec) has a coefficient of thermal expansionof 307 ppm/K and a storage elastic modulus of 2.18 MPa. The outer layerwas formed of the same material as that of the intermediate layer.

An autoclave process was performed on the laminate at a temperature ofabout 110° C. and a pressure of about 2 atm to manufacture an opticaldevice having the structure of FIG. 1. The total thickness of theintermediate layers in the optical device of Example 1 is about 1,520μm.

Example 2

An optical device was manufactured by performing the process in the samemanner as in Example 1, except that the first intermediate layer waschanged into a single layer of the TPU layer (Argotec), one layer ofwhich had a thickness of about 380 μm, and the second intermediate layerwas changed into a laminate of two TPU layers (Argotec), one layer ofwhich had a thickness of about 380 μm. The total thickness of theintermediate layers in the optical device of Example 2 is about 1,140μm.

Example 3

An optical device was manufactured by performing the process in the samemanner as in Example 1, except that the first intermediate layer waschanged into a laminate of two TPU layers (Argotec), one layer of whichhad a thickness of about 380 μm, and the second intermediate layer waschanged into a single layer of the TPU layer (Argotec), one layer ofwhich had a thickness of about 380 μm. The total thickness of theintermediate layers in the optical device of Example 3 is about 1,140μm.

Example 4

An optical device was manufactured by performing the process in the samemanner as in Example 1, except that the first intermediate layer waschanged into a laminate of two TPU layers (Argotec), one layer of whichhad a thickness of about 380 μm, and the second intermediate layer waschanged into a laminate of three TPU layers (Argotec), one layer ofwhich had a thickness of about 380 μm. The total thickness of theintermediate layers in the optical device of Example 4 is about 1,900μm.

Example 5

An optical device was manufactured by performing the process in the samemanner as in Example 1, except that the first intermediate layer waschanged into a laminate of three TPU layers (Argotec), one layer ofwhich had a thickness of about 380 μm, and the second intermediate layerwas changed into a laminate of two TPU layers (Argotec), one layer ofwhich had a thickness of about 380 μm. The total thickness of theintermediate layers in the optical device of Example 5 is about 1,900μm.

Example 6

An optical device was manufactured by performing the process in the samemanner as in Example 1, except that the first intermediate layer and thesecond intermediate layer were each changed into a laminate of three TPUlayers (Argotec), one layer of which had a thickness of about 380 μm.The total thickness of the intermediate layers in the optical device ofExample 6 is about 2,280 μm.

Comparative Example 1

An optical device was manufactured by performing the process in the samemanner as in Example 1, except that the first intermediate layer and thesecond intermediate layer were each changed into a single layer of theTPU layer, one layer of which had a thickness of about 380 μm. The totalthickness of the intermediate layers in the optical device ofComparative Example 1 is about 760 μm.

Evaluation Example 1. Evaluation of pressing and crowding defects

In the optical devices manufactured in Examples 1 to 6 and ComparativeExample 1, it was observed whether pressing and crowding defectsoccurred in a state where no voltage was applied. In Example 1, thepressing defects and the crowding defects were not observed, but inComparative Example 1, the pressing and crowding defects were observed,as shown in FIGS. 3A and 3B. As shown in FIG. 3A, the crowding defectregion appears darker than the peripheral region because theconcentration of the dichroic dye is higher than that of the peripheralregion, and as shown in FIG. 3B, the pressing defect region appearsbrighter than the peripheral region because the concentration of thedichroic dye is lower than that of the peripheral region.

TABLE 1 Total thickness of Evaluation of pressing intermediate layers(μm) and crowding defects Example 1 1,520 Good Example 2 1,140 GoodExample 3 1,140 Good Example 4 1,900 Good Example 5 1,900 Good Example 62,280 Good Comparative 760 Fault Example 1

EXPLANATION OF REFERENCE NUMERALS

100 a: first outer substrate, 100 b; second outer substrate, 200 a, 200b: intermediate layer, 300: liquid crystal element, 400: outer layer, 10a: first base layer, 10 b: first electrode layer, 10 c:pressure-sensitive adhesive layer, 20 a: second base layer, 20 b: secondelectrode layer, 20 c: spacer, 20 d: alignment film.

1. An optical device comprising: a first outer substrate; a second outer substrate; a liquid crystal element positioned between the first outer substrate and the second outer substrate; a first intermediate layers positioned between the first outer substrate and the liquid crystal element; and a second intermediate layer positioned between the second outer substrate and the liquid crystal element, wherein a sum of total thicknesses of the first and second intermediate layers is 800 μm or more, and wherein the liquid crystal element comprises: a first base layer; a second base layer; a liquid crystal layer positioned between the first base layer and the second base layer, wherein the liquid crystal layer comprises a liquid crystal compound and a dichroic dye; a pressure-sensitive adhesive layer positioned between the first base layer and the liquid crystal layer; and wherein the spacer maintains a gap between the first and second base layers.
 2. The optical device according to claim 1, wherein the first outer substrate and the second outer substrate are each a glass substrate.
 3. The optical device according to claim 1, wherein the optical device does not have polarizers between the first outer substrate and the liquid crystal element and between the second outer substrate and the liquid crystal element.
 4. The optical device according to claim 1, wherein the optical device further comprises one or more polarizers, wherein the one or more polarizers are positioned in at least one of between the first outer substrate and the liquid crystal element or between the second outer substrate and the liquid crystal element.
 5. The optical device according to claim 1, wherein the pressure-sensitive adhesive layer has a storage modulus in a range of 0.01 MPa to 1 MPa.
 6. The optical device according to claim 1, wherein the liquid crystal layer is capable of switching between a first orientation state and second orientation state different from the first orientation state when external energy is applied.
 7. The optical device according to claim 1, wherein the dichroic dye is present in an amount of 0.2 wt % to 10 wt %, based on the total weight of the liquid crystal layer.
 8. The optical device according to claim 1, wherein the spacer is a patterned spacer.
 9. The optical device according to claim 1, wherein a ratio of an area (B) of the spacer to an area (A) of the second base layer is in a range of 5% to 50%.
 10. The optical device according to claim 1, wherein the liquid crystal element further comprises: a first electrode layer formed on an inner surface of the first base layer; and a second electrode layer formed on an inner surface of the second base layer, where the pressure-sensitive adhesive layer is present on an inner surface of the first electrode layer, and wherein the spacer is present on an inner surface of the second electrode layer.
 11. The optical device according to claim 10, wherein the liquid crystal element further comprises: an alignment film present on the inner surface of the second electrode layer, where the inner surface of the first electrode layer does not have an alignment film formed thereon.
 12. The optical device according to claim 1, wherein each of the first and second intermediate layers have a thickness in a range of 400 μm to 3,000 μm.
 13. The optical device according to claim 1, wherein each of the first and second intermediate layers have a storage elastic modulus in a range of 1 MPa to 100 MPa.
 14. The optical device according to claim 1, wherein each of the first and second intermediate layers have a Young's modulus in a range of 0.1 MPa to 100 MPa.
 15. The optical device according to claim 1, wherein each of the first and second intermediate layers have a coefficient of thermal expansion of 2,000 ppm/K or less.
 16. The optical device according to claim 1, wherein each of the first and second intermediate layers are a thermoplastic polyurethane adhesive layer, a polyamide adhesive layer, a polyester adhesive layer, an EVA (ethylene vinyl acetate) adhesive layer, an acrylic adhesive layer, a silicone adhesive layer, or a polyolefin adhesive layer.
 17. An automobile, comprising: a vehicle body having an opening formed therein; and the optical device of claim 1 mounted in the opening. 